Serpentinite

Summary

Serpentinite is a rock composed predominantly of one or more serpentine group minerals, the name originating from the similarity of the texture of the rock to that of the skin of a snake.[1] Serpentinite has been called serpentine or serpentine rock, particularly in older geological texts and in wider cultural settings.[2][3][4][5][6]

Serpentinite from the Maurienne valley, Savoie, French Alps
Sample of serpentinite from the Golden Gate National Recreation Area, California, United States
Chromitic serpentinite (7.9 cm (3.1 in) across), Styria Province, Austria. Protolith was a Proterozoic-Early Paleozoic upper mantle dunite peridotite that has been multiply metamorphosed during the Devonian, Permian, and Mesozoic.
Tightly folded serpentinite from the Tux Alps, Austria. Closeup view about 30 cm × 20 cm (11.8 in × 7.9 in).

Formation and mineralogyEdit

Serpentinite is formed by near to complete serpentinization of mafic to ultramafic rocks.[7] Serpentinite can be formed wherever ultramafic rock is infiltrated by water poor in carbon dioxide.[8] This occurs at mid-ocean ridges and in the forearc mantle of subduction zones.[9][10]


The final mineral composition of serpentinite is usually dominated by lizardite, chrysotile, and magnetite. Brucite and antigorite are less commonly present. Lizardite, chrysotile, and antigorite all have approximately the formula Mg3(Si2O5)(OH)4 or (Mg2+, Fe2+)3Si2O5(OH)4, but differ in minor components and in form.[9] Accessory minerals, present in small quantities, include awaruite, other native metal minerals, and sulfide minerals.[11]

 
Ophiolite of the Gros Morne National Park, Newfoundland. Ophiolites characteristically have a serpentinite component.

Hydrothermal vents and mud volcanoesEdit

 
A white carbonate spire in the Lost City vent field

Deep sea hydrothermal vents located on serpentinite close to the axis of mid-ocean ridges generally resemble black smokers located on basalt, but emit complex hydrocarbon molecules. The Rainbow field of the Mid-Atlantic Ridge is an example of such hydrothermal vents. Serpentinization alone cannot provide the heat supply for these vents, which must be driven mostly by magmatism. However, the Lost City Hydrothermal Field, located off the axis of the Mid-Atlantic Ridge, may be driven solely by heat of serpentinization. Its vents are unlike black smokers, emitting relatively cool fluids (40 to 75 °C (104 to 167 °F)) that are highly alkaline, high in magnesium, and low in hydrogen sulfide. The vents build up very large chimneys, up to 60 meters (200 ft) in height, composed of carbonate minerals and brucite. Lush microbial communities are associated with the vents. Though the vents themselves are not composed of serpentinite, they are hosted in serpentinite estimated to have formed at a temperature of about 200 °C (392 °F).[12] Sepiolite deposits on mid-ocean ridges may have formed through serpentinite-driven hydrothermal activity.[13] However, geologists continue to debate whether serpentinization alone can account for the heat flux from the Lost City field.[12]

The forearc of the Marianas subduction zone hosts large serpentinite mud volcanoes, which erupt serpentinite mud that rises through faults from the underlying serpentinized forearc mantle. Study of these mud volcanoes gives insights into subduction processes, and the high pH fluids emitted at the volcanoes support a microbial community.[14][10]

Serpentinite thermal vents are a candidate for the environment in which life on Earth originated.[14] Most of the chemical reactions necessary to synthesize acetyl-CoA, essential to basic biochemical pathways of life, take place during serpentinization.[15] The sulfide-metal clusters that activate many enzymes resemble sulfide minerals formed during serpentinization.[16]

Experimental drilling into the gabbro layer of oceanic crust near mid-ocean ridges has demonstrated the presence of a sparse population of hydrocarbon-degrading bacteria. These may feed on hydrocarbons produced by serpentinization of the underlying ultramafic rock.[17][18]

EcologyEdit

 
Serpentinite ecosystem in the south of New Caledonia

Soil cover over serpentinite bedrock tends to be thin or absent. Soil with serpentine is poor in calcium and other major plant nutrients, but rich in elements toxic to plants such as chromium and nickel.[19] Some species of plants, such as Clarkia franciscana and certain species of manzanita, are adapted to living on serpentinite outcrops. However, because serpentinite outcrops are few and isolated, their plant communities are ecological islands and these distinctive species are often highly endangered.[20] On the other hand, plant communities adapted to living on the serpentine outcrops of New Caledonia resist displacement by introduced species that are poorly adapted to this environment.[21]

Serpentine soils are widely distributed on Earth, in part mirroring the distribution of ophiolites and other serpentine bearing rocks. [22] There are outcroppings of serpentine soils in the Balkan Peninsula, Turkey, the island of Cyprus, the Alps, Cuba, and New Caledonia. In North America, serpentine soils also are present in small but widely distributed areas on the eastern slope of the Appalachian Mountains in the eastern United States, and in the Pacific Ranges of Oregon and California.[citation needed]

OccurrencesEdit

Notable occurrences of serpentinite are found at Thetford Mines, Quebec; Lake Valhalla, New Jersey; Gila County, Arizona; Lizard complex, Lizard Point, Cornwall; and in localities in Greece, Italy, and other parts of Europe.[23] Notable ophiolites containing serpentinite include the Semail Ophiolite of Oman, the Troodos Ophiolite of Cyprus, the Newfoundland ophiolites, and the Main Ophiolite Belt of New Guinea.[24]

UsesEdit

Decorative stone in architecture and artEdit

 
Drinking cups, evidences of serpentinite turning in Zöblitz

Serpentine group minerals have a Mohs hardness of 2.5 to 3.5, so serpentinite is easily carved.[25] Grades of serpentinite higher in calcite, along with the verd antique (breccia form of serpentinite), have historically been used as decorative stones for their marble-like qualities. College Hall at the University of Pennsylvania, for example, is constructed out of serpentine. Popular sources in Europe before contact with the Americas were the mountainous Piedmont region of Italy and Larissa, Greece.[26] Serpentinites are used in many ways in the arts and crafts. For example, the rock has been turned in Zöblitz in Saxony for several hundred years.[27]

Carving stone tools, oil lamp-known as the Qulliq and Inuit sculptureEdit

The Inuit and other indigenous people of the Arctic areas and less so of southern areas used the carved bowl shaped serpentinite qulliq or kudlik lamp with wick, to burn oil or fat to heat, make light and cook with. The Inuit made tools and more recently carvings of animals for commerce.[28]

Swiss ovenstoneEdit

A variety of chlorite talc schist associated with Alpine serpentinite is found in Val d'Anniviers, Switzerland and was used for making "ovenstones" (German: Ofenstein), a carved stone base beneath a cast iron stove.[29]

Neutron shield in nuclear reactorsEdit

Serpentinite has a significant amount of bound water, hence it contains abundant hydrogen atoms able to slow down neutrons by elastic collision (neutron thermalization process). Because of this serpentinite can be used as dry filler inside steel jackets in some designs of nuclear reactors. For example, in RBMK series, as at Chernobyl, it was used for top radiation shielding to protect operators from escaping neutrons.[30] Serpentine can also be added as aggregate to special concrete used in nuclear reactor shielding to increase the concrete density (2.6 g/cm3 (0.094 lb/cu in)) and its neutron capture cross section.[31][32]

CO2 sequestrationEdit

Because it readily absorbs carbon dioxide, serpentinite may be of use for sequestering atmospheric carbon dioxide.[33] To speed the reaction, the serpentinite may be reacted with carbon dioxide at elevated temperature in carbonation reactors. Carbon dioxide may also be reacted with alkaline mine waste from serpentine deposits, or carbon dioxide may be injected directly into underground serpentinite formations.[34] Serpentinite may also be used as a source of magnesium in conjunction with electrolytic cells for CO2 scrubbing.[35]

Cultural referencesEdit

It is the state rock of California, USA and the California Legislature specified that serpentine was "the official State Rock and lithologic emblem."[3] In 2010, a bill was introduced which would have removed serpentine's special status as state rock due to it potentially containing chrysotile asbestos.[36] The bill met with resistance from some California geologists, who noted that the chrysotile present is not hazardous unless it is mobilized in the air as dust.[37][needs update]

See alsoEdit

ReferencesEdit

  1. ^ Schoenherr, Allan A. (11 July 2017). A Natural History of California: Second Edition. Univ of California Press. pp. 35–. ISBN 9780520295117. Retrieved 6 May 2017.
  2. ^ "serpentine". Merriam-Webster.com Dictionary. Merriam-Webster. Retrieved 6 March 2022.
  3. ^ a b California Government Code § 425.2; see "CA Codes (Gov:420-429.8)". Archived from the original on 28 June 2009. Retrieved 24 December 2009.
  4. ^ Oakeshott, G.B. (1968). "Diapiric Structures in Diablo Range, California". AAPG Special Volume M8:Diapirism and Diapirs. 153: 228–243.
  5. ^ Flett, J.S. (1913). "The geology of the lizard". Proceedings of the Geologists' Association. 24 (3): 118–133. doi:10.1016/S0016-7878(13)80008-9.
  6. ^ González-Mancera, G.; Ortega-Gutiérrez, F.; Nava, N.E.; Arriola, H.S. (2003). "Mössbauer Study of Serpentine Minerals in the Ultramafic Body of Tehuitzingo, Southern Mexico". Hyperfine Interactions. 148 (1–4): 61–71. Bibcode:2003HyInt.148...61G. doi:10.1023/B:HYPE.0000003765.32151.3b. S2CID 96761317.
  7. ^ "Introduction to Mineralogy and Petrology". ScienceDirect. Retrieved 20 November 2022.
  8. ^ Moody 1976, p. 136.
  9. ^ a b Roberts, B. A.; Proctor, J. (6 December 2012). The Ecology of Areas with Serpentinized Rocks: A World View. Springer Science & Business Media. p. 8. ISBN 978-94-011-3722-5.
  10. ^ a b Albers, Elmar; Bach, Wolfgang; Pérez-Gussinyé, Marta; McCammon, Catherine; Frederichs, Thomas (2021). "Serpentinization-Driven H2 Production From Continental Break-Up to Mid-Ocean Ridge Spreading: Unexpected High Rates at the West Iberia Margin". Frontiers in Earth Science. 9. doi:10.3389/feart.2021.673063/full. ISSN 2296-6463.
  11. ^ Moody, Judith B. (April 1976). "Serpentinization: a review". Lithos. 9 (2): 125–138. Bibcode:1976Litho...9..125M. doi:10.1016/0024-4937(76)90030-X.
  12. ^ a b Allen, Douglas E.; Seyfried, W.E. (March 2004). "Serpentinization and heat generation: constraints from Lost City and Rainbow hydrothermal systems 1 1Associate editor: J. C. Alt". Geochimica et Cosmochimica Acta. 68 (6): 1347–1354. doi:10.1016/j.gca.2003.09.003.
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  16. ^ McCollom, T. M.; Seewald, J. S. (1 April 2013). "Serpentinites, Hydrogen, and Life". Elements. 9 (2): 129–134. CiteSeerX 10.1.1.852.2089. doi:10.2113/gselements.9.2.129. Retrieved 5 September 2021.
  17. ^ Mason, Olivia U.; Nakagawa, Tatsunori; Rosner, Martin; Van Nostrand, Joy D.; Zhou, Jizhong; Maruyama, Akihiko; Fisk, Martin R.; Giovannoni, Stephen J. (5 November 2010). "First Investigation of the Microbiology of the Deepest Layer of Ocean Crust". PLOS ONE. 5 (11): e15399. Bibcode:2010PLoSO...515399M. doi:10.1371/journal.pone.0015399. PMC 2974637. PMID 21079766.
  18. ^ Marshall, Michael (17 November 2010). "Life is found in deepest layer of Earth's crust". New Scientist. Retrieved 3 December 2021.
  19. ^ "CVO Website - Serpentine and serpentinite" Archived 19 October 2011 at the Wayback Machine, USGS/NPS Geology in the Parks Website, September 2001, accessed 27 February 2011.
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  21. ^ "La flore de Nouvelle-Calédonie – Première partie". Futura-sciences.com. 18 August 2004. Retrieved 30 January 2013.
  22. ^ academic.oup.com https://academic.oup.com/book/41004/chapter-abstract/349244500?redirectedFrom=fulltext. Retrieved 20 November 2022. {{cite web}}: Missing or empty |title= (help)
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  24. ^ Philpotts & Ague 2009, p. 371.
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  26. ^ Ashurst, John. Dimes, Francis G. Conservation of building and decorative stone. Elsevier Butterworth-Heinemann, 1990, p. 51.
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  28. ^ Kerr, A.; Squires, G.C. "Serpentinites and associated rock types near Hopedale, Nunatsiavut: Potential for artisanal carving-stone resources" (PDF). Geological Survey Report. Newfoundland and Labrador Department of Natural Resources. 19 (1): 39–57. Retrieved 3 September 2021.
  29. ^ Talcose-schist from Canton Valais. By Thomags Bonney, (Geol. Mag., 1897, N.S., [iv], 4, 110--116) abstract
  30. ^ Lithuanian Energy Institute (28 May 2011). "Design of structures, components, equipments and systems". Ignalina Source Book. Archived from the original on 9 October 2011. Retrieved 28 May 2011.
  31. ^ Aminian, A.; Nematollahi, M.R.; Haddad, K.; Mehdizadeh, S. (3–8 June 2007). Determination of shielding parameters for different types of concretes by Monte Carlo methods (PDF). ICENES 2007: International Conference on Emerging Nuclear Energy Systems. Session 12B: Radiation effects. Istanbul, Turkey. p. 7. Archived from the original (PDF) on 3 March 2016. Retrieved 28 May 2011.
  32. ^ Abulfaraj, Waleed H.; Salah M. Kamal (1994). "Evaluation of ilmenite serpentine concrete and ordinary concrete as nuclear reactor shielding". Radiation Physics and Chemistry. 44 (1–2): 139–148. Bibcode:1994RaPC...44..139A. doi:10.1016/0969-806X(94)90120-1. ISSN 0969-806X.
  33. ^ Farhang, F.; Oliver, T.K.; Rayson, M.S.; Brent, G.F.; Molloy, T.S.; Stockenhuber, M.; Kennedy, E.M. (March 2019). "Dissolution of heat activated serpentine for CO2 sequestration: The effect of silica precipitation at different temperature and pH values". Journal of CO2 Utilization. 30: 123–129. doi:10.1016/j.jcou.2019.01.009. S2CID 104424416.
  34. ^ Power, I. M.; Wilson, S. A.; Dipple, G. M. (1 April 2013). "Serpentinite Carbonation for CO2 Sequestration". Elements. 9 (2): 115–121. doi:10.2113/gselements.9.2.115.
  35. ^ Li, Wenzhi; Li, Wen; Li, Baoqing; Bai, Zongqing (February 2009). "Electrolysis and heat pretreatment methods to promote CO2 sequestration by mineral carbonation". Chemical Engineering Research and Design. 87 (2): 210–215. doi:10.1016/j.cherd.2008.08.001.
  36. ^ Fimrite, Peter (16 July 2010). "Geologists protest bill to remove state rock". San Francisco Chronicle. Retrieved 17 April 2018.
  37. ^ Frazell, Julie; Elkins, Rachel; O'Geen, Anthony; Reynolds, Robert; Meyers, James. "Facts about Serpentine Rock and Soil Containing Asbestos in California" (PDF). ANR Catalog. University of California Division of Agriculture and Natural Resources. Retrieved 17 April 2018.

External linksEdit